Growing investigations into HM Revenue and Customs employees who deliberately disclosed data without authorisation, have resulted in both dismissal and prosecution, the department has confirmed.

Responding to a report, which highlighted ministerial revelations of a year on year rise in investigations against staff, a spokesman pointed to “improved detection and heightened awareness” as an explanation for the increase in investigations, when asked if more staff were breaking the rules.

But staff who did act improperly were said to have faced repercussions with HMRC’s data security policy taken “extremely seriously” by the department.

The spokesman said HMRC had “robust rules in place to prevent staff making unauthorised disclosures of data”.

And as part of measures available to the department, Treasury minister David Gauke had said it was “possible” for staff to be prosecuted if found to have breached the Data Protection Act or the Commissioners for Revenue and Customs Act.

HMRC confirmed that proven cases of unauthorised disclosure had led to disciplinary action “including dismissal and prosecution”.

Gauke revealed last week that a total of 35 HMRC staff had been investigated for deliberate data breaches since 2007, the year when HMRC was caught up in the loss of 25 million child benefit records.